1. Field of the Invention
The invention is related to the field of nanometer-scale imprinting and, in particular, to a resist material having self-releasing properties that is used in nanometer-scale imprinting processes.
2. Statement of the Problem
Nanoimprint lithography is a high-throughput method for imprinting nanometer-scale patterns on a substrate. One particular use for nanoimprint lithography is for manufacturing disk drives. Disk drive manufacturers strive to increase the recording density of drive systems. One way to increase the recording density is to pattern the surface of the magnetic disk to form discrete data tracks, referred to as discrete track recording (DTR). A magnetic disk utilizing DTR typically includes a series of concentric raised zones, which are referred to herein as pillars, providing a medium for storing data.
To imprint the nanometer-scale patterns on a substrate (i.e., a substrate for a magnetic disk), a master tool is first fabricated having a desired pattern. The master tool is not typically used for imprinting an actual substrate as it can be quickly worn out when a large number of imprints are needed. The master tool is expensive and time consuming to fabricate, so the master tool instead is used to fabricate a plurality of stamper tools. The stamper tools are actually used for imprinting the substrates (i.e., replicating the pattern on the stamper tools on the substrates).
To fabricate a stamper tool, the master tool is pressed into a layer of resist material to imprint the inverse pattern of the master tool in the resist layer. Heat or ultraviolet (UV) irradiation may then be applied to cure the resist layer in the inverse pattern of the master tool, which forms a cured resist layer. The master tool is then removed from the cured resist layer leaving a stamper tool having a desired pattern. The stamper tool may then be used to imprint a plurality of substrates.
To imprint a substrate, the stamper tool is pressed into a thin layer of resist material deposited on the substrate to imprint the inverse pattern of the stamper tool in the resist layer. Heat or UV irradiation may then be applied to cure the resist layer in the inverse pattern of the stamper tool, forming a cured resist layer. The stamper tool is then separated from the cured resist layer which leaves a substrate with a desired resist pattern covering the substrate. An etching process, such as Reactive Ion Etching (RIE), may then be performed to pattern the substrate according to the resist pattern. A similar process is performed to replicate the pattern in many substrates using the stamper tool.
When the stamper tool is pressed into a resist layer and the resist layer is cured, some of the cured resist layer may stick to the stamper tool. The stamper tool (and also the master tool) may be referred to generally herein as a “template”. The resist layer and the template have relatively high surface energies, and the adhesion between the cured resist layer and the template is greater than the cohesion of the resist layer itself. The resist layer fractures internally leaving behind a residue of resist material which obscures the nanometer-scale features on the template. To avoid problems of having residue stick to the template, a release layer is formed on the template from some type of anti-adhesion material. The release layer has anti-adhesion properties (low surface energy and low friction) so that the resist material will not stick to the template when it is separated from the resist layer, as the cured resist layer needs to be perfectly separated from the template without leaving behind any residue and with the smallest possible force required to accomplish the separation.
Unfortunately, problems still exist in present nano-imprint processes. Even though release layers are used, the adhesion force between the template and the cured resist layer remains high. This high adhesion force acts to incrementally remove the release layer from the template as the template is used for replication. Because a template is used for many replications, the release layer can be quickly worn away. The result is residue sticking to the template, which obscures the nanometer-scale features on the template.